Human psoriasis lesions and imiquimod-induced psoriasiform dermatitis manifest the enhanced expression of IL-17-related inflammatory or proliferative markers, such as IL-17A/C/F, IL-22, TNF-α, IL-1β, IL-6, keratin 16, and the reduced expression of regulatory or anti-proliferative markers, such as IL-10, transforming growth factor (TGF)-β1, cyclin-dependent kinase inhibitor (CDKN) 1A [1], and the abundant infiltration of CD3+ T cells and Ly6G+ neutrophils and increase in Ki67+ proliferating epidermal keratinocytes [22], and are associated with the defects of Foxp3+ Tregs [4]. Here, IL17A is linked to psoriasis.